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Subject: Re: [virtio-comment] Re: [PATCH 3/3] shared memory: Define mmio registers
* Stefan Hajnoczi (stefanha@redhat.com) wrote: > On Fri, Jan 11, 2019 at 11:42:00AM +0000, Dr. David Alan Gilbert (git) wrote: > > diff --git a/content.tex b/content.tex > > index 776162a..e2435ff 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -1641,6 +1641,33 @@ All register values are organized as Little Endian. > > selected by writing to \field{QueueSel}. > > } > > \hline > > + \mmioreg{SHMSel}{Shared memory region select}{0x0b0}{W}{% > > + Writing to this register selects the shared memory region \ref{sec:Basic Facilities of a Virtio Device / Shared Memory Regions} > > + following operations on \field{SHMId}, \field{SHMLenLow}, \field{SHMLenHigh}, > > + \field{SHMBaseLow} and \field{SHMBaseHigh} apply to. The index > > + number of the first region is zero (0x0); note that it is a > > + simple index that does not correspond to the \field{id}. > > Why use a separate virtio-mmio index instead of the shared memory ID? > The driver would map those IDs it knows about, so I'm not sure if > enumerating them via a separate index is useful. Plus using the ID lets > you drop one register from the interface. Yes, I think if we don't need enumeration that's right; we just shange SHMId to be the writeable register and drop the SHMSel register. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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